I have a Speed Demon on an Airgap but never had the problems you describe just a blown power valve that took me too long to figure out.

My four mixture screws are just one turn out and the Idle Eze is open 1.5 turns, the baseline setting.
My fuel level is just below middle on the sight glass.
Do you have an open plenum, I use a one inch four hole spacer, makes throttle response really crisp ?

Is that manifold on a SBF? My manifold is a square-bore. I think it would make a difference in the casting where the carb meets it. My mixture screws are a half turn more rich than yours. My float levels are a little bit higher than the middle line of the sight glass which I know is a bit richer than they suggest. I have no spacer on the manifold. With my EZ idle screw bottomed out the carb is not letting in any un-metered air into the motor. Yes my A/F meter is a good reference point - like I said when I noticed the problem I changed the BG back to my 750cfm VS Holley and the meter ran true in the greens (slightly rich) where I like it for best acceleration.